That used to bother me as a student. Maybe I’ve just grown accustomed to it.

But reconsidering it now, the placement says to square the function, so I think that’s why it works. It’s important to stress that sine is a function to students, otherwise they think they can “distribute” when they see sin(x+y). (It’s kind of ironic. All the time students get stuck with distributing in algebra, but suddenly when they see trig where they can’t, they finally recognize it…)

Some of the expressions in particle physics get so convoluted we write s sub theta as short hand for sin(theta). Then we write s sub theta exponent 2. That’s a lot cleaner. 🙂